Alpha-aminomethylene phosphonate betaines and polymers prepared therewith

ABSTRACT

Alpha-aminoethylene phosphonate betaines of the formula ##STR1## R 1  is hydrogen or methyl; X is ##STR2## a is 0, 1, 2 or 3, with the condition that when X is ##STR3##  that a be greater than 1; R 2  and R 3  are independently C 1  -C 6  alkyl, aryl, benzyl, or cyclohexyl; 
     Y is hydrogen or hydroxyl; 
     b is 0, 1, 2, or 3; 
     Z is C 1  -C 6  alkyl, aryl, benzyl, cyclohexyl, or ##STR4##  and M is hydrogen, metallic cation, or ammonium ion are disclosed as are homo- and copolymers thereof.

This application is a division of application Ser. No. 940,701, filedDec. 11, 1986, now U.S. Pat. No. 4,707,306.

The present invention relates to alpha-aminomethylene phosphonatebetaines and to polymers prepared therewith. In particular, theinvention relates to monomers having the general formula: ##STR5## R¹ ishydrogen or methyl; X is ##STR6## a is 0, 1, 2, or 3, with the conditionthat when X is ##STR7## that a be greater than 1; R² and R³ areindependently C₁ -C₆ alkyl, aryl, benzyl, or cyclohexyl;

Y is hydrogen or hydroxyl;

b is 0, 1, 2, or 3;

Z is C₁ -C₆ alkyl, aryl, benzyl, cyclohexyl, or ##STR8## and M ishydrogen, metallic cation, or ammonium ion.

Also disclosed herein are homopolymers of these betaines as well ascopolymers thereof prepared with any ethylenically unsaturatedcopolymerizable comonomer.

These alpha-aminomethylene phosphonate betaines are useful in a varietyof applications including soil anti-redeposition agents in detergents,chelating agents for scale inhibition, as crystal modifiers and in oilwell drilling needs.

The monomeric betaines are prepared by the reaction of a compound of thegeneral structure ##STR9## where R¹, X, a, R², and R³ are as definedabove with compounds of the following general structures: ##STR10##where L is halogen or ##STR11## with R⁴ being alkyl or aryl; and Y, b,Z, and M are as defined above.

The reaction of these compounds is carried out in a suitable aqueoussolvent (usually water or alcohol/water) at a pH of 7-9 and atemperature of 10°-90° C. Under such conditions the reaction issubstantially complete in one-half to ten hours, preferably one to fivehours. The solution may be acidified with mineral acid if the acid formof the monomer, (where M is hydrogen), is desired.

If bisphosphonomethylchloroethyl amine is used as the compound ofFormula III, the reaction is carried out at a pH of about 7-9 obtainedby the addition of sodium hydroxide, preferably pH 8, and a temperatureof 20°-60° C., preferably about 50° C. This reaction is carried outunder atmospheric pressures and is substantially completed within aperiod of about 3 hours. Using this starting material, the resultingbetaine will correspond to formula I where y is H, Z is --CH₂ --PO(ONa)₂and b is O.

In order to produce compounds of formula I where Y is OH, b is 1 or 2,and Z is --CH₂ --PO(OH)₂, chlorohydroxypropyl (or butyl)bisphosphonomethylamine is used as the compound of Formula III and thereaction is carried out at a pH of about 6 to 8, preferably about pH 7,using the same temperature and other conditions described previously.

Isolation of the monomers is difficult owing to their hygroscopicnature. However, these compounds may be isolated by evaporation of thereaction solvent to give a thick syrup. The syrup is then lyophilized togive the monomer in dry form.

Generally, the monomer solution obtained by the above described reactionis used directly in conventional free radical emulsion or solutionpolymerization procedures. The betaine monomers may be homopolymerizedor copolymerized with up to 99% by weight, preferably at least 50% byweight of an ethylenically unsaturated comonomer or mixture ofcomonomers.

Representative comonomers include acrylic or methacrylic acids andesters thereof with C₁ -C₁₈ alcohols; unsaturated carboxylic acids suchas itaconic and maleic acids and esters thereof, (meth)acrylamide andtheir N-substituted derivatives, such as N-mono and N-dimethyl, -ethyl,-propyl, and -butyl acrylamide or methacrylamide and N-mono ordiphenylacrylamide; vinyl esters such as vinyl acetate or vinylpropionate; vinyl ethers such as butyl vinyl ether; N-vinyl lactams suchas N-vinyl pyrrolidinone; halogenated vinyl compounds such as vinylchloride and vinylidene chloride or fluoride; alkyl vinyl ketones suchas methyl or ethyl vinyl ketone; diesters such as dimethyl, diethyl,dipropyl, dibutyl, diphenyl, dibenzyl, and di(phenylethyl) itaconate,maleate, and fumarate; and polyethyleneglycol acrylate or methacrylateor polypropyleneglycol acrylate or methacrylate.

Also useful herein are minor amounts (e.g., 0.01 to about 2%) ofmultifunctional crosslinking monomers. Representative of suitablecrosslinkers are those containing a multiplicity of ethylenicallyunsaturated units per molecule such as diallyl maleate, triallylcyanurate, tetraethylene glycol dimethyacrylate, hexa-allyl sucrose,etc.

The polymerization is initiated by a free radical initiator such asperacid or salt thereof, e.g., hydrogen peroxide, sodium peroxide,lithium peroxide, peracetic acid, persulfuric acid or the ammonium andalkali metal salts thereof, e.g. ammonium persulfate, sodium peracetate,lithium persulfate, potassium persulfate, sodium persulfate, t-butylperacetate, etc. Various azo compounds may also be used,azobisisobutyronitrile, for example. A suitable concentration of theinitiator is from 0.05 to 10 weight percent and preferably from 0.1 to 3weight percent.

The free radical initiator can be used alone and thermally decomposed torelease the free radical initiating species or can be used incombination with a suitable reducing agent in a redox couple. Thereducing agent is typically an oxidizable sulfur compound such as analkali metal metabisulfite and pyrosulfite, e.g. sodium metabisulfite.

If emulsion polymerization procedures are employed, the emulsifyingagent is generally any of the nonionic oil-in-water surface activeagents or mixtures thereof generally employed in emulsion polymerizationprocedures. When combinations of emulsifying agents are used, it isadvantageous to use a relatively hydrophobic emulsifying agent incombination with a relatively hydrophilic agent. The amount ofemulsifying agent is generally from about 1 to about 10, preferably fromabout 2 to about 8, weight percent of the monomers used in thepolymerization.

The emulsifier used in the polymerization can also be added, in itsentirety, to the initial charge or a portion of the emulsifier, e.g.from 90 to 25 percent thereof, can be added continuously orintermittently during polymerization.

The preferred interpolymerization procedure is a modified batch processwherein the major amounts of some or all the comonomers and emulsifierare charged to the reaction vessel after polymerization has beeninitiated. In this manner, control over the copolymerization of monomershaving widely varied degrees of reactivity can be achieved. It ispreferred to add a small portion of the monomer emulsion initially andthen the remainder of the monomer emulsion intermittently orcontinuously over the polymerization period which can be from 0.5 toabout 10 hours, preferably from about 1 to about 5 hours.

The resulting polymeric emulsion or solution contains 10 to 80%,preferably about 30 to 60% solids, by weight. It may be used directly orthe polymer may be recovered in solid form using the procedure describedfor isolation of the monomer or well-known spray-drying techniques.Using the above described procedure, the polymer is produced at a yieldof at least about 90% conversion.

An alternative method for the production of the betaine polymer involvesfirst the polymerization of the tertiary amine monomer with subsequentquarternization of the polymer with phosphonomethylamine reagent. Morespecifically, these polymers are synthesized by first polymerizing amonomer of the general structure ##STR12## where R¹, X, a, R², and R³are as defined above to give a homopolymer or, if other ethylenicallyunsaturated comonomers are used, a copolymer. The resultant polymers canbe represented by the general structure: ##STR13## where R¹, X, a, R²,and R³ are as previously defined, n and m are positive integers, and Ais a repeating unit derived from one or more ethylenically unsaturatedcomonomers. These polymers are then reacted with a compound of generalstructure ##STR14## under conditions analogous to those previouslydescribed for the monomer preparation.

The resulting derivatized polymers can be represented by the generalstructure ##STR15## where R¹, X, a, R², R³, Y, b, Z, M, n, A, and m areas previously defined. In the latter case, the reagents, reactionconditions and isolation procedures for the quaternization aresubstantially the same as those described previously however the yieldsare in the range of about 50 to 70% conversion.

The following examples are presented to illustrate but not to restrictthe present invention. Parts and percentages are by weight andtemperatures in degrees Celsius unless otherwise noted.

EXAMPLE 1

This example illustrates the preparation of haloalkylaminomethylenediphosphonic acid from haloalkylamines, formaldehyde and phorphorousacid. These acids correspond generally to Formula III where Y ishydrogen, L is chlorine and Z is methylene phosphoic acid. Thesecompounds were made according to the procedure of K. Moedritzer and R.R. Irani, J. Org. Chem. 31 1603 (1966).

A 2 liter flask was equipped with a mechanical stirrer, thermometer,condenser, heating mantle, and addition funnel. Phosphorous acid (164.0g, 2.0 mol), water (300 ml), and 2-chloroethylamine hydrochloride(115.99 g, 1.0 ml) were charged to the flask, and concentratedhydrochloric acid (300 ml) added. The reaction mixture was brought toreflux and formalin solution (324.3 g, 37% solution, 4.0 mol) was addedover 1 hour. After the addition was complete the reaction mixture wasrefluxed an additional 2 hours. The reaction mixture was concentrated togive a thick syrup. Ethanol (275 ml) was added to inducecrystallization. The product was filtered and dried to give a whitepowder. Repetitions of this procedure resulted in yields of 205 to 240grams (76-90% conversion).

EXAMPLE 2

This example illustrates the preparation ofhaloalkylaminoalkylmethylenephosphonic acids from N-haloalkyl, N-alkylamines, formaldehyde, and phosphorous acid. These compounds correspondto Formula III where L is chlorine, Y is hydrogen and Z is methyl. Thesecompounds were made also according to the procedure of K. Moedritzer andR. R. Irani, J. Org, Chem 31 1603 (1966).

A 2 liter flask was equipped with a mechanical stirrer, thermometer,condenser heating mantle, and addition funnel. Phosphorous acid (82.2 g,1.00 mol), N-2-chloroethyl, N-methylamine hydrochloride (130.1 g, 1.0mol), and water (260 ml) were charged to the flask. Concentratedhydrochloric acid (300 ml) was added slowly. The reaction mixture washeated to reflux and formalin solution (159.6 g, 37% solution, 2.0 mol)was added over 1 hour. After the addition was complete, the reactionmixture was held an reflux an additional 2 hours.

As noted by Moedritzer and Irani, crystallization cannot easily beinduced. A solution of the product in water (total solution weight 240g) gave 4.10 meg of organic chloride per gram. Conductometric titrationof the product solution yielded three equivalence points, indicatingthat the product exists as the hydrochloride salt of the aminomethylenephosphonic acid.

EXAMPLE 3

This example describes a two step synthesis for the preparation ofhalohydroxyalkylaminomethylenediphosphonic acids fromalkenylaminomethylenediphosphonic acids, elemental halogen, and water.These compounds correspond to Formula III where L is chlorine, Y ishydroxyl, and Z is --CH₂ --PO(OH)₂. (It will be recognized by thoseskilled in the art that during the reaction of the above compounds ofFormula III where Y is hydroxyl and L is halogen with the compounds ofFormula II, compounds of Formula IV will be produced as intermediates.)

The alkenylaminomethylenediphosphonic acids were synthesized fromalkenylamines, formaldehyde, and phosphorous acid in the mannerdescribed in Example 1.

A 500 ml flask was equipped with a mechanical stirrer, condenser, gasdispersion tube, thermometer, and water bath.Allylaminomethylenediphosphonic acid (100. g, 0.408 mol) and water (100ml) were charged to the flask and partial dissolution occurred. Chlorinegas (31.9 g, 0.449 mol) was bubbled sub-surface into the reactionmixture through the gas dispersion tube. The temperature during thechlorine addition was controlled at 30° C. The resulting solution of3-chloro-2-hydroxypropylaminomethylenediphosphonic acid weighed 240 gand contained 1.7 meg of organic chloride per gram. The solution can beconcentrated to yield the product as a white solid, but is generallyused directly.

EXAMPLE 4

This example describes the preparation ofalpha-aminomethylenephosphonate betaines from reaction ofN-dialkylaminoalkyl acrylamides or 2-substituted acrylamides with thehaloalkylaminomethylenediphosphonic acids of Example 1. This compoundcorresponds to one of Formula I where Y is H, Z is --CH₂ --PO(OH)₂, b isO, R₁, R₂ and R₃ are --CH₃, X is CONH and a is 3.

A 2 liter flask was equipped with a mechanical stirrer, thermometer,condenser, addition funnel, and a pH probe.2-Chloroethylaminomethylenediphosphonic acid (267.5 g, 1.0 mol) andwater (350 ml) were slurried in the reactor.Dimethylaminopropylmethacrylamide (170.1 g, 1.0 mol) was addedportionwise. A solution of sodium hydroxide (120.0 g, 3.0 mol) in H₂ O(180 ml) was added to the mixture slowly. The temperature of thereaction mixture was raised to 50° C. and the reaction allowed tocontinue for 3 hours, at which time analysis for chloride ion indicatedthat the reaction was substantially complete.

EXAMPLE 5

This example illustrates the preparation ofalpha-aminomethylenephosphonate betaines from reaction ofN-dialkylaminoalkyl acrylates or 2-substituted acrylates with thehalohydroxyalkylaminomethlenediphosphonic acids of Example 3. Theresulting monomers correspond to those of Formula I where X is CO₂, a is2, R₁, R₂, and R₃ are --CH₃, y is OH, b is 1, and Z is --CH₂ --PO(OH)₂.

A 2 liter flask was equipped with a mechanical stirrer, thermometer,condenser, addition funnel, and a pH probe.3-Chloro-2-hydroxypropylaminomethylenediphosphonic acid (148.8 g, 0.5mol) and H₂ O (150 ml) were charged to the flask.Dimethylaminoethylmethacrylate (78.5 g, 0.5 mol) was charged to theflask portionwise. A solution of sodium hydroxide (60.0 g, 1.5 mol) inH₂ O (90 ml) was added slowly with stirring. The temperature of thereaction mixture was raised to 50° C. and the reaction mixture stirredfor 3 hours, at which time analysis for chloride ion indicated that thereaction was substantially complete.

EXAMPLE 6

This example illustrates the copolymerization of the betaine monomerfrom Example 4 with acrylic acid in aqueous isopropanol.

A 500 ml flask was equipped with a stirrer, condenser, addition funnels,heating mantle, and thermometer. Isopropanol (910 g) and water (88 ml)were charged to the flask and brought to reflux. A monomer charge ofacrylic acid (57.6 g) and a 44% solution of the betaine monomer fromExample 4 (239.0 g) was added continuously over 3 hours. An initiatorcharge of sodium persulfate (3.6 g) dissolved in H₂ O (16.4 ml) wasadded simultaneously with the monomer charge over 3 hours. After theadditions were complete, the polymer solution was refluxed for 1 hour.The isopropanol was removed by distillation, then the polymer solutionwas cooled and discharged from the reactor.

This polymer was characterized as follows:

Mw=45,716

Mn=3,571.

After exhaustive dialysis against water, the polymer was analyzed fornitrogen and phosphorus content:

    ______________________________________                                                    Calculated                                                                            Observed                                                  ______________________________________                                        % N           5.30      5.93                                                  % P           7.85      7.01                                                  ______________________________________                                    

EXAMPLE 7

This example illustrates the copolymerization of betaine monomer fromExample 4 with acrylic acid in water with sodium hydrophosphite present.

A 2 liter flask was equipped with a stirrer, condensor, additionfunnels, heating mantle, nitrogen purge, and thermometer. Water (2.62ml) and sodium hypophosphite (38.4 g) were charged to the flask andheated to 75° C. A monomer charge of acrylic acid (285. g) and a 30.8%solution of the betaine monomer from Example 4 (62.11 g) was addedcontinuously over 2 hours. Simultaneously, an initiator charge of sodiumpersulfate (7.5 g) is H₂ O (70 ml) was added over 21/2 hours. When theinitiator addition was complete the reaction temperature was raised to85° and the reaction mixture stirred for 2 hours. The polymer was thencooled and discharged from the reactor.

This polymer was characterized as follows: Mw=2820; Mn=1280; % P is 3.81(calculated) and 2.47 (observed).

EXAMPLE 8

This example describes an alternative method for the preparation ofpolymers containing pendant alpha-aminomethylenephosphonate betainestructures from polymers containing tertiary amines andhaloalkylaminomethylenediphosphonic acid.

A tertiary amine-containing polymer is prepared as follows: A 500 mlflask was equipped with a stirrer, condenser, thermometer, additionfunnels, and hot water bath. Isopropanol (70 g) and water (110 ml) wereadded and brought to reflux. A monomer solution of acrylic acid (57.6g), dimethylaminopropylmethacrylamide (34.0 g), and water (20 ml) wereadded over 3 hours. Simultaneously, an initiator solution of ammoniumpersulfate (5. g) in water (25 ml) was added over 3 hours. When theadditions were complete, the polymer solution was held at reflux for 1hour, the isopropanol removed by distillation, then the polymer solutioncooled and discharged from the reactor. The polymer concentration wasadjusted with water to 40%.

The resulting solution (145.5 g at 40%; 0.120 mole polymeric tertiaryamine) was charged to a 500 ml flask equipped with stirrer, thermometer,addition funnel, condenser, and hot water bath.2-Chloroethylaminomethylenediphosphonic acid (32.1 g, 0.120 mol) wasadded and the temperature raised to 50° C. Sodium hydroxide (132. g, 3.3mol) in water 200 ml) was slowly added. The mixture was stirred for 3hours at 50° C. After exhaustive dialysis against water the polymer wasanalyzed for phosphorous and nitrogen:

    ______________________________________                                                    Calculated                                                                            Observed                                                  ______________________________________                                        % N           4.97      5.94                                                  % P           7.32      4.31                                                  ______________________________________                                    

EXAMPLE 9

This example illustrate the preparation of polymers containing pendantalpha-aminomethylene phosphonate betaine structures from polymerscontaining tertiary amines and haloalkylaminoalkyl methylenediphosphonic acids in non-aqueous media.

A tertiary amine-containing polymer was prepared as follows: A 2 literflask was equipped with a stirrer, condenser, thermometer, additionfunnels, and hot water bath. Ethanol (180.0 g), benzoyl peroxide (3.0g), methyl methacrylate (15.0 g) butyl methacrylate (3.0 g), anddimethyl aminopropyl methacrylamide (12.0 g) were charged to the flaskand heated to reflux. A monomer solution of methyl methacrylate (135.0g), butyl methacrylate (27.0 g), dimethylaminopropylmethacrylamide(108.0 g) in ethanol (160.0 g) and an initiator solution of benzoylperoxide (3.8 g) in ethanol (105.0 g) were added continuously over 4hours. After the additions were complete, the reaction mixture was heldat reflux for an additional 2 hours. A second initiator solution oft-butylperpivalate (2.0 g) in ethanol (30.0 g) was added over 1/2 hourand the solution was then refluxed an additional hour.

The resulting solution (275 g at 36.3%, 0.235 mole polymeric tertiaryamine) was charged to a 1 liter flask equipped with a stirrer,condenser, thermometer, addition funnel, and hot water bath. A solutionof N-(2-chloroethyl)-N-methyl-amino methylene phosphosphonic acid (111.9g at 47.1% in ethanol, 0.235 mol) was added and the reaction mixtureheated to 50° C. Ethanolic potassium hydroxide (144.2 g at 25%, 0.642mole) was added dropwise over 1 hour. The reaction mixture was heated at50° C. for 1 hour, then cooled.

The resulting polymer was completely soluble in water, in contrast tothe total water insolubility of the parent butyl methacrylate/methylmethacrylate/dimethylaminopropylmethacrylamide polymer. Dialyzed againstwater, the polymer was analyzed for phosphorus and nitrogen:

    ______________________________________                                                    Calculated                                                                            Observed                                                  ______________________________________                                        % N           6.62      5.70                                                  % P           4.89      4.33                                                  ______________________________________                                    

EXAMPLE 10

This example illustrates an emulsion polymerization procedure for thepreparation of polymers containing pendantalpha-aminomethylenephosphonate betaine structures.

A 2-L flask is equipped with a stirrer, condenser, thermometer,additional funnels, hot water bath, and nitrogen purge. Ethoxylatednonyl phenol (6.9 g), water (192.0 g) and t-butylhydroperoxide (0.06 g)are charged to the flask. The pH of this initial charge is adjusted to4.0 using acetic acid. With agitation a pre-emulsified mixture of ethylacrylate (475.0 g), betaine monomer (Example 1, 38%, 132 g), water (55.0g), ethoxylated nonylphenol (54.5 g), and t-butylhydroperoxide (0.6) isadded at 60° over 4 hours. Simultaneously, a solution of sodiumformaldehyde sulfoxylate (0.6 g) in water (20 g) is added. The resultingemulsion polymer is coagulated and washed with water. The washed-polymeris analyzed for phosphorus content.

    ______________________________________                                                    Calculated                                                                            Observed                                                  ______________________________________                                        % P           1.0       0.10                                                  % N           0.44      0.05                                                  ______________________________________                                    

EXAMPLE 11

This example illustrates the preparation of the betaine analog fromdimethylaminopropylmethacrylamide andchloro-hydroxypropyl-bisphosphonomethylamine.

The procedure of Example 5 was repeated using 288 grams of a 51.7%solution of chloro-hydroxypropyl-bisphosphonomethylamine and 85 grams ofdimethylaminopropylmethacrylamide with the pH adjusted to 7 with 150grams of a 40% solution of sodium hydroxide.

The resulting betaine (52.3% solids) was used directly in apolymerization with acrylic acid using the procedure of Example 3 with144 grams acrylic acid and 533 grams of the betaine solution.

Analysis of the dialyzed polymer gave the following:

    ______________________________________                                                    Calculated                                                                            Observed                                                  ______________________________________                                        % P           10.3      7.26                                                  % N           6.21      5.57                                                  ______________________________________                                    

Now that the preferred embodiments of the present invention have beendescribed in detail, various modifications and improvements thereon willbecome readily apparent to those skilled in the art. Accordingly, thespirit and scope of the present invention is to be limited only by theappended claims, and not by the foregoing disclosure.

We claim:
 1. Copolymers comprising up to 99% by weight of analpha-aminomethylene phosphonate betaine of the formula: ##STR16## whereR¹ is hydrogen or methyl;X is ##STR17## a is 0, 1, 2, or 3, with thecondition that when X is ##STR18## that a be greater than 1; R² and R³are independently C₁ -C₆ alkyl, aryl, or cyclohexyl; Y is hydrogen orhydroxyl; b is 0, 1, 2, or 3; Z is C₁ -C₆ alkyl, aryl, cyclohexyl, or##STR19## and M is hydrogen, metallic cation, or ammonium ion and atleast 1% by weight of an ethylenically unsaturated comonomer.
 2. Thecopolymers of claim 1 wherein the ethylenically unsaturated comonomer isselected from the group consisting of acrylic or methacrylic acids andesters thereof with C₁ -C₁₈ alcohols; unsaturated dicarboxylic acids andesters thereof; (meth)acrylamide and their N-substituted derivatives;vinyl esters; vinyl ethers; N-vinyl lactams; halogenated vinylcompounds; alkyl vinyl ketones; and polyethyleneglycol orpolypropyleneglycol acrylate or methacrylate.
 3. The copolymers of claim2 wherein the comonomer is acrylic or methacrylic acid or an esterthereof.
 4. The copolymer of claim 3 wherein the comonomer is acrylicacid.
 5. The copolymer of claim 1 wherein the ethylenically unsaturatedcomonomer is present in an amount greater than 50% by weight.
 6. Thecopolymer of claim 2 wherein the ethylenically unsaturated comonomer ispresent in an amount greater than 50% by weight.
 7. The copolymer ofclaim 1 additionally containing up to 2% by weight of a multifunctionalcrosslinking monomer.
 8. The copolymer of claim 7 wherein themultifunctional crosslinking monomer is selected from the groupconsisting of diallyl maleate, triallyl cyanurate, tetraethylene glycoldimethacrylate, and hexa-allyl sucrose.
 9. Homopolymers prepared fromalpha-aminomethylene phosphonate betaine monomers of the formula:##STR20## where R¹ is hydrogen or methyl;X is ##STR21## a is 0, 1, 2, or3, with the condition that when X is ##STR22## that a be greater than 1;R² and R³ are independently C₁ -C₆ alkyl, aryl, or cyclohexyl; Y ishydrogen or hydroxyl; b is 0, 1, 2, or 3; Z is C₁ -C₆ alkyl, aryl,cyclohexyl, or ##STR23## and M is hydrogen, metallic cation, or ammoniumion.